Hydrological dynamics of water sources in a Mediterranean lagoon

Abstract

Abstract. Lagoons are important ecosystems occupying large coastal areas worldwide. Lagoons contain various mixtures of marine and freshwater sources which are highly dynamic in time. However, it often remains a challenge to identify and quantify dynamic changes of water sources, particularly in heterogeneous lagoon systems like the Köycegiz-Dalyan lagoon (KDL), which is located at the south-west of Turkey on the Mediterranean Sea coast. The objective of this study was to quantify different contributions of potential water sources i.e. surface water, groundwater and seawater in the lagoon and how these water sources changed over time and space. In the wet-and dry-season stable isotopes of water, chloride concentration (Cl − ) and salinity were measured in two depths in the lagoon and surrounding water bodies (sea, lake, groundwater). Different components of water sources were quantified with a three component endmember mixing analysis. Differences in Cl − and stable isotopes over time indicated the dynamic behaviour of the system. Generally, none of the groundwater samples was impacted by water of the Mediterranean Sea. During the wet season, most of the lagoon water (> 95 %) was influenced by freshwater and vertically well mixed. During the dry season, high Cl − in the deeper sampling locations indicated a high contribution of marine water throughout the entire lagoon system due to saltwater intrusion. However, a distinct layering in the lagoon was obvious from low Cl − and depleted isotope contents close to the surface supporting freshwater inflow into the system even during the dry season. Besides temporal dynamics also spatial heterogeneities were identified. Changes in water sources were most evident in the main lagoon channel compared to more isolate lagoon lakes, which were influenced by marine water even in the wet season, and compared to side branches indicating slower turnover times. We found that environmental tracers helped to quantify highly dynamic and heterogeneous contributions of different water sources in the Köycegiz-Dalyan lagoon.

Groundwater flow processes and mixing in active volcanic systems: the case of Guadalajara (Mexico)

“…Although all studies show a similar trend, the data reported by IMTA (1992) registered heavier δ 18 O values that may be attributable to evaporation or hydrothermal influence. Similar δ 18 O values in thermal systems have been reported in other studies, e.g., El-Fiky (2009) and Stumpp et al (2014), with δ 18 O values ranging from −6.7 to −5.6 and −4.8 to +0.8 ‰, respectively. Hydrothermal groundwater collected in Toluquilla, has a narrow range of δ 18 O (−9.4 to −8.8 ‰) and δ 2 H (−67 to −68 ‰) values.…”

“…The combination of different environmental tracer techniques helps elucidate the groundwater's origin, recharge, flow velocity and direction, residence or travel times, connections between aquifers, and surface and groundwater interrelations (Edmunds and Smedley, 2000;De Vries and Simmers, 2002;Appelo and Postma, 2005;Ako et al, 2013;Stumpp et al, 2014). These techniques have been applied in large semiarid to arid rift systems (Bretzler et al, 2011;Furi et al, 2011;Ghiglieri et al, 2012;Siebert et al, 2012;Panno et al, 2013;Forrest et al, 2013;Williams et al, 2013).…”

Groundwater flow processes and mixing in active volcanic systems: the case of Guadalajara (Mexico)

“…Atemajac and Toluquilla valleys consist of a relatively thin cover of Quaternary lacustrine deposits overlying a thick section of Neogene volcanic rocks including silicic domes, lava and cinder cones, lithic tuffs, basalts, ignimbrites and other pyroclastic rocks, andesites and volcanic breccia, and a basement consisting of Oligocene granite (Gutiérrez-Negrín, 1988;Urrutia et al, 2000;Campos-Enríquez et al, 2005) ( Fig. 2).…”

“…The combination of different environmental tracer techniques helps elucidate the groundwater's origin, recharge, flow velocity and direction, residence or travel times, connections between aquifers, and surface and groundwater interrelations (Edmunds and Smedley, 2000;De Vries and Simmers, 2002;Appelo and Postma, 2005;Ako et al, 2013;Stumpp et al, 2014). These techniques have been applied in large semiarid to arid rift systems (Bretzler et al, 2011;Furi et al, 2011;Ghiglieri et al, 2012;Siebert et al, 2012;Panno et al, 2013;Forrest et al, 2013;Williams et al, 2013).…”

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“…Many studies were performed about water quality (Ekdal, 2008;Özçelik, 2015), dynamics (Bayarı, Kurttaş, & Tezcan, 2001;Gönenç, et al, 2004;Stumpp, Ekdal, Gönenç, & Maloszewski, 2014) and biodiversity (Kazancı, Oğuzkurt, Girgin., & Dügel, 2003;Akın, Buhan, Winemiller, & Yılmaz, 2005;Balık, Ustaoğlu, Sarı, İlhan, & Topkara, 2005;Saygılı, Yiğit, & Bulut, 2011) of Köyceğiz Lagoon. However, limited studies on fishes inhabited the ecosystem and fishing practised, are available.…”